Many diagnostic and therapeutic medical procedures require navigating a medical device to a particular location through lumens in the body. For example, procedures such as cardiac catheterizations and interventional neuroradiology procedures involve the introduction of medical devices through the arteries; bronchoscopies involve the introduction of medical devices through the trachea; endoscopies and colonoscopies involve the introduction of instruments through the gastrointestinal tract; and urethroscopies involve the introduction of medical devices through the urinary tract.
Numerous methods and apparatus have been developed for introducing medical devices in the body. Many of these methods employ guide wires for remotely controlling the orientation of the tip of the medical device as it is advanced in the body lumen. These guide wires typically have a bend in their distal ends, the tip is rotated until the tip is properly oriented, and the wire is then advanced. It is a difficult and tedious process to steer a medical device remotely with a guide wire since the orientation of the guide wire is difficult to control. Thus, these procedures can be prolonged, which increases the risk to the patient and fatigues the physician.
It has been proposed to guide medical devices in the body with magnets, see Yodh, Pierce, Weggel, and Montgomery, A New Magnetic System, for ‘Intravascular Navigation’, Medical & Biological Engineering, Vol. 6, No. 2, pp. 143–147 (March 1968), incorporated herein by reference. This article proposes a magnetically tipped catheter that is steered within the body by an externally applied magnetic field. However, the magnet in this proposed device is attached to the catheter which can impair the ability to control the magnet. Moreover, there is no provision for removing the magnet and leaving the catheter or other medical device in place. Thus, only one such catheter can be directed to a given position because the magnetic field acting on one magnet will also act on the other magnets in the vicinity.